Tumors originating from the chest wall are uncommon in dogs; however, osteosarcomas and chondrosarcomas arising from the ribs are frequently documented among these cases (1,12,14,15). Unless infiltration into the soft tissues is extensive, tumors originating in the ribs do not require en bloc resection of the skin and overlying muscles (12). After rib resection, chest wall reconstruction can be achieved using the latissimus dorsi muscle flap and polypropylene mesh (1,11-13).

Soft tissue sarcoma (STS) arising in the chest wall has been documented in the medical literature; however, few case reports detailing its treatment exist. These tumors typically require en bloc resection extending from the skin to the chest wall, requiring a 3-cm lateral margin (12). However, when performing wide-margin resection in the case of a relatively large STS in a small dog, preserving the skin and muscles for chest wall reconstruction becomes challenging (12,13).

Several analyses have been conducted to identify the prognostic factors that affect the survival rate of patients with STS. Of these factors, the histological grade is considered the most critical for predicting recurrence (16,17). Recent studies in both veterinary and human medicine have proposed that the extent of resection has limited effects on disease-free intervals and overall survival, leading to a transition towards less radical approaches with a focus on preserving function (2-4,8,16,17).

This article presents a case report of the surgical removal of a grade 2 STS originating from the chest wall of a small dog. The surgical approach included full-thickness resection with a 1-cm lateral margin to enable primary wound closure for chest wall reconstruction and to maximize the preservation of respiratory function.

A 4-year-old, 9 kg, spayed female French Bulldog was referred to the Jeju National University Veterinary Teaching Hospital for evaluation and surgical resection of a left-sided chest wall tumor. Physical examination revealed that the tumor was firmly adhered to the skin and subcutaneous tissue on the left side of the chest wall. Blood tests showed no abnormalities in complete blood count and serum chemistry levels. Prior to the operation, a punch biopsy was conducted on a portion of the lesion and histopathological analysis was performed. Examination of the requested specimen resulted in the diagnosis of grade 2 STS. Radiography and computed tomography (CT) were performed to assess tumor size, extent of invasion, and presence of metastasis to other organs. The tumor size was 6.5 × 5.7 × 3.5 cm and had deeply penetrated the tissue, contacting the ninth rib (Fig. 1). No evidence of metastasis to other organs was found. Our surgical plan included en bloc resection involving full-thickness excision, encompassing the eighth to tenth ribs, with lateral margins set 1 cm from the tumor’s edge to enable primary wound closure. Chemotherapy was planned for the patient after surgery.

Figure 1. Computed tomography of the chest wall region. A well-circum^- scribed mass is visible in the left side chest wall region, exhibiting infiltration into the thoracic muscles and ribs without involvement of internal organs. The tumor measures 65 mm in diameter.

The dog was premedicated with midazolam 0.2 mg/kg intravenously (IV) (Midazolam Inj^®; Bukwang Pharm, Korea). Anesthesia was induced using propofol 4 mg/kg (IV) (Anepol Inj^®; Hana Pharm, Korea), followed by endotracheal intubation. Respiratory anesthesia was maintained with isoflurane (Ifran^®; Hana Pharm, Korea). Cefazoline 20 mg/kg (IV) (Cefazoline Injection^®; Chongkundang, Korea), a prophylactic antibiotic, was administered prior to operation. Intraoperative analgesia was provided by continuous rate infusion of remifentanil (0.01 mg/kg/h, Remiva Inj^®; Hana Pharm, Korea), lidocaine (1 mg/kg/h, Lidocaine Hcl Hydrate Inj. 2%^®; Daihan, Korea), and ketamine (0.12 mg/kg/h, Ketamine 50 Inj^®; Yuhan, Korea), which is collectively referred to as RLK. The dog was positioned in right lateral recumbency and hair clipping was performed as widely as possible, including at the surgical site (Fig. 2A). A 1-cm margin was marked around the tumor using a sterile pen (Fig. 2B). An incision was made along the marked border, and the tissue under the skin was incised perpendicular to the designated margins. The tumor was invasively located beneath the skin. Latissimus dorsi muscle was extensively removed from the chest wall along with the tumor (Fig. 3A). Macroscopically, the tissue surrounding the ninth rib appeared to share blood vessels with the tumor. Therefore, the eighth, ninth, and tenth ribs were resected en bloc with the planned surgical margins using bone cutters and scissors (Fig. 3B). The organs within the exposed thoracic cavity did not exhibit macroscopic tumor invasion (Fig. 3C). Before closing the defect, a chest tube was placed through the twelfth intercostal space (Fig. 3D). Polypropylene mesh (Marlex^®; Davol Inc, USA) was used to reconstruct the defective chest wall. Mesh wider than the defect area was used. At the boundary of the deficient chest wall, the mesh was double-folded to enhance suture fixation using non-absorbable circumcostal sutures. The mesh was stretched to provide rigidity (Fig. 4A). The residual part of the latissimus dorsi and cutaneous trunci muscles were sutured together and placed over the mesh (Fig. 4B). Subsequently, the subcutaneous tissue was sutured using absorbable sutures and the skin was sutured using a medical stapler.

Figure 2. Patient with grade 2 soft tissue sarcoma on the left side chest wall. (A) Wide-area hair clipping was performed, including around the surgical site. (B) A sterile pen was used to mark a 1-cm margin around the tumor.

Figure 3. Surgical resection of chest wall soft tissue sarcoma. (A) The tumor was excised from the chest wall, including a significant portion of the latissimus dorsi muscle. (B) The eighth, ninth, and tenth ribs were resected en bloc with the planned surgical margins, using bone cutters. (C) Organs within the exposed thoracic cavity did not display macroscopic evidence of tumor invasion. (D) Prior to closing the surgical site, a chest tube was inserted through the twelfth intercostal space.

Figure 4. Chest wall reconstruction following surgical resection of soft tissue sarcoma. (A) Mesh reinforcement at the chest wall defect boundary, double-folded for improved suture fixation using non-absorbable circumcostal sutures. The mesh was stretched to enhance rigidity. (B) Suturing of the remaining latissimus dorsi and cutaneous trunci muscles together and placed over the mesh.

During postoperative hospitalization, a continuous-rate infusion of RLK was maintained for pain management, and cefazoline was administered intravenously three times a day. The dog exhibited an appetite starting the day after the operation, and no respiratory compromise was observed postoperatively. On the day after the operation, pleural effusion through the chest tube decreased to less than 1 mL/kg/day. However, negative pressure in the thoracic cavity was not sustained, leading to pneumothorax. On the third postoperative day, as the negative pressure within the thoracic cavity was sustained and the pneumothorax resolved, the chest tube was removed and the dog was discharged.

The resected tumor was diagnosed postoperatively as grade 2 STS. The tumor regionally infiltrated the surrounding fibroadipose tissue and extended to the lateral margins. Tumors were also detected in the soft tissues of the removed ribs; however, no evidence of tumor invasion into the bones was observed.

The skin staples were removed two weeks after the operation, and the dog experienced no adverse effects. The dog’s owner did not want to initiate chemotherapy immediately and decided to pursue follow-up care instead. No evidence of metastasis or signs of local recurrence were detected within the first three months after the operation.

This study did not select the traditional 3-cm lateral margin resection for the treatment of invasive STS of the chest wall. The rationale for this decision is detailed below. Traditionally, STS treatment involves wide-margin resection to eliminate all tumor cells that could potentially lead to local recurrence (5,6). This approach is theoretically sound as numerous studies have shown that wide-margin surgery for the treatment of STS significantly reduces local recurrence and mortality rates (5,6). However, recent studies have raised questions about the exclusive influence of surgical margins on the outcomes of conventional STS surgical approaches (2-4,8,16,17). In one study, dogs demonstrated 100% local disease control and 93% one-year disease free interval using a 1-cm lateral margin approach for STS removal with a one-year follow-up period (2). Moreover, another study demonstrated local recurrence rates of 7% for grade 1, 34% for grade 2, and 75% for grade 3 for marginally excised STS, emphasizing the significant impact of tumor histological grade on local recurrence rates (16). In our case, the patient was diagnosed with grade 2 STS based on preoperative biopsy findings. We devised a surgical plan with reference to this modified STS treatment paradigm. Another important consideration is the possibility of primary wound closure after chest wall tumor resection (9,13). Reconstruction to improve the structural stability of the chest after tumor removal is essential to minimize postoperative complications and mortality (9,11-13). In this patient, the tumor was significantly larger than the area of the chest wall. If wide surgical margins had been employed, it could have presented challenges for primary wound closure, potentially leading to the onset of rapid respiratory dysfunction. Taking these factors into account, we formulated a surgical plan involving full-thickness resection with a 1-cm lateral margin. Additionally, we established the option of initiating postoperative chemotherapy as needed to treat any remaining tumor cells.

Commonly employed methods for chest wall reconstruction after rib resection involve muscle flaps or polypropylene mesh (1,7,9,11-15). In cases of rib tumors, extensive removal of the skin and latissimus dorsi muscle is not required unless substantial invasion into the surrounding soft tissues has occurred. Thus, chest wall reconstruction with a latissimus dorsi muscle flap can be utilized (12). In this case, a significant portion of the latissimus dorsi and cutaneous trunci muscles were removed. Additionally, the tumor was observed near one of the ribs and shared blood vessels, leading to the decision to perform rib resection. The defect area was reconstructed using polypropylene mesh, and the remaining muscles were sutured together and placed over the mesh to enhance stability because of the reported high incidence of side effects associated with using mesh-alone (1,13).

When performing reconstruction with polypropylene mesh, frequently reported wound complications include infection, dehiscence, seroma, hematoma, and soft tissue necrosis, with one study indicating a 6.7% incidence of these complications (13). No complications were observed in this patient.

After thoracotomy, elevated intrathoracic pressure makes it difficult for the lungs to expand normally; therefore, a chest tube must be inserted to drain exudate and air from the chest cavity to restore lung function (1,11-13,15). Typically, the chest tube can be removed when the exudate volume falls below 5 mL/kg/day, and negative pressure in the chest is maintained for 12-24 h (13). Although the exudate through the chest tube was less than 1 mL/kg/day starting the day after the operation, achieving stable negative pressure in the thoracic cavity required 72 h in this patient.

Thoracotomy is a painful procedure, and effective postoperative pain management is essential because it can hinder deep breathing and coughing, potentially affecting the recovery of lung function (10-12). In human medicine, epidural analgesia is considered the gold standard for post-thoracotomy pain management, as intravenous opioid administration may lead to adverse effects, such as respiratory depression and cough suppression, rendering it less suitable for thoracotomy patients (10). However, the patient recovered without significant breathing obstruction after a continuous intravenous opioid infusion.

This case report presents a detailed description of the surgical treatment of STS occurring in the chest wall and the subsequent postoperative care. One limitation of this study was that the owner did not choose the initially planned postoperative chemotherapy despite the postoperative biopsy evaluation indicating incomplete histological margins. Although complete surgical margins have been shown to contribute to reduced tumor recurrence and patient mortality in the surgical removal of STS arising from the chest wall, recent evidence suggests that relying solely on wide surgical margins may not be justified. Treatment decisions must be made with careful consideration of the patient’s overall well-being and functional preservation.

The patient was diagnosed with grade 2 STS based on a preoperative biopsy. The surgical plan included full-thickness resection with a 1-cm lateral margin, allowing primary wound closure and preservation of respiratory function to the greatest extent possible. Chest wall reconstruction was subsequently accomplished using polypropylene mesh, with the remaining muscles sutured together and positioned over the mesh. Postoperative biopsy revealed a grade 2 STS with incomplete histological margins. Nonetheless, the patient exhibited a remarkably rapid recovery following the operation, and no signs of metastasis or local recurrence were detected during the 3-month follow-up period.

The authors have no conflicting interests.